Polymerizable liquid-crystalline compounds

ABSTRACT

Polymerizable liquid-crystalline compounds of the formula I 
     
         Z.sup.1 --Y.sup.1 --A.sup.1 --Y.sup.3 --M--Y.sup.4 --A.sup.2 --Y.sup.2 
    
      --Z 2                                                  I 
     where 
     Z 1  and Z 2  are radicals containing reactive groups via which polymerization can be effected, 
     Y 1  -Y 4  are a single chemical bond, oxygen, sulfur, --O--CO--, --CO--O--, --O--CO--O--, --CO--NR--, --NR--CO--, --O--CO--NR--, --NR--CO--O-- or --NR--CO--NR--, where at least one of the groups Y 3  and Y 4  is --O--CO--O--, --O--CO--NR--, --NR--CO--O-- or --NR--CO--NR--, 
     A 1  and A 2  are spacers having 2 to 30 carbon atoms in which the carbon chain may be interrupted by ether oxygen, thioether sulfur or by nonadjacent imino or C 1  -C 4  -alkylimino groups, 
     M is a mesogenic group, 
     R is C 1  -C 4  -alkyl, 
     and compositions comprising them are distinguished by favorable liquid-crystalline phase-temperature ranges and can be used in optical display devices and in cholesteric liquid-crystalline colorants.

BACKGROUND OF THE INVENTION

This application is a 371 of PCT/EP96/03756, filed Aug. 26, 1996.

1. Field of the Invention

The present invention relates to novel polymerizable liquid-crystallinecompounds of the formula I

    Z.sup.1 --Y.sup.1 --A.sup.1 --Y.sup.3 --M--Y.sup.4 --A.sup.2 --Y.sup.2 --Z.sup.2                                                 I

where

Z¹ and Z² are radicals containing reactive groups via whichpolymerization can be effected,

Y¹ -Y⁴ are a single chemical bond, oxygen, sulfur, --O--CO--, --CO--O--,--O--CO--O--, --CO--NR--, --NR--CO--, --O--CO--NR--, --NR--CO--O-- or--NR--CO--NR--, where at least one of the groups Y³ and Y⁴ is--O--CO--O--, --O--CO--NR--, --NR--CO--O-- or --NR--CO--NR--,

A¹ and A² are spacers having 2 to 30 carbon atoms in which the carbonchain may be interrupted by ether oxygen, thioether sulfur or bynonadjacent imino or C₁ -C₄ -alkylimino groups,

M is a mesogenic group,

R is C₁ -C₄ -alkyl.

The present invention furthermore relates to liquid-crystal compositionscomprising these compounds and possibly one or more chiral compounds, toa process for preparing the novel liquid-crystalline compounds, to aprocess for coating substrates with the novel compounds orliquid-crystal compositions, and to the use of the compounds orliquid-crystal compositions for producing optical display devices, ascholesteric liquid-crystalline colorants, and to pigments obtainable bypolymerizing the liquid-crystal compositions and subsequentlycomminuting.

2. Description of the Background

Numerous compounds are not converted directly into the liquid, unorderedstate on warming from the crystalline state with a defined close andlong-distance ordering of the molecules, but instead pass through aliquid-crystalline phase, in which, although the molecules are mobile,the molecule axes form an ordered structure. Elongate moleculesfrequently form nematic liquid-crystalline phases which arecharacterized by an alignment long-distance ordering owing to parallelarrangement of the long axes of the molecules. If a nematic phase ofthis type contains chiral compounds, a so-called cholesteric phaseforms, which is characterized by a helical superstructure of the longaxes of the molecules. The chiral compound here can be theliquid-crystalline compound itself or it can be added to a nematicliquid-crystalline phase as a chiral dope.

Liquid-crystalline materials have remarkable optical properties based onthier anisotropic ordered state. However, the liquid-crystalline orderedstate only occurs in a limited temperature range. The temperature rangein which liquid-crystalline phases occur is frequently far above thedesired use temperature or extends only over a small temperature range.

There are various ways of obtaining and fixing the ordering structuresdesired for the material properties, even in the solid state. Inaddition to glass-like solidification on cooling from theliquid-crystalline state, there is also the possibility ofcopolymerization into polymeric networks or, if the liquid-crystallinecompounds contain polymerizable groups, polymerization of theliquid-crystalline compounds themselves.

Polymerizable liquid-crystalline compounds are described, for example,in EP-A 261 712 and in WO 93/05436, WO 95/24453, WO 95/24454 and WO95/24455. In polymeric form, these compounds usually have the requisitemechanical stabilities, but are in some cases unsatisfactory owing tothe temperature level of their liquid-crystalline phases and thetemperature range of these phases.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide polymerizableliquid-crystalline compounds or liquid-crystal compositions which havelow liquid-crystalline phase temperatures, broad liquid-crystallinephase ranges and, in the polymeric state, good mechanical strength andfixing of the liquid-crystalline ordered state.

We have found that this object is achieved by the polymerizableliquid-crystalline compounds and liquid-crystal compositions comprisingthe latter described at the outset.

DETAILED DESCRIPTION OF THE INVENTION

For the purposes of the present invention, polymerization is taken tomean all reactions in which polymers are built up, ie. additionpolymerization as a chain reaction, addition polymerization as astepwise reaction and condensation polymerization.

Preferred radicals Z¹ and Z² are the following: ##STR1## where theradicals R are identical or different C₁ -C₄ -alkyl.

Of the reactive polymerizable groups, the cyanates can trimerizespontaneously to form cyanurates and are therefore preferred.Polymerization of compounds containing epoxide, thiirane, aziridine,isocyanate and isothiocyanate groups requires further compoundscontaining complementary reactive groups. For example, isocyanates canpolymerize with alcohols to form urethanes and with amines to form ureaderivatives. An analogous situation applies to thiiranes and aziridines.The complementary reactive groups can either be present in a secondnovel compound, which is mixed with the first, or they can be introducedinto the polymerization mixture by means of auxiliary compoundscontaining two or more of these complementary groups. If these compoundsin each case contain two of these reactive groups, linear polymershaving a predominantly thermoplastic character are formed. If thecompounds contain more than two reactive groups, crosslinked polymerswhich are particularly mechanically stable are formed. The maleimidogroup is particularly suitable for free-radical copolymerization witholefinic compounds such as styrene.

Preferred polymerizable groups Z¹ and Z² are those which are susceptibleto free-radical polymerization, ie. in particular olefinicallyunsaturated groups, and of these the groups ##STR2## are of particularimportance in combination with Y¹ and Y².

The moieties Z¹, Z², A¹, A², M and X in the novel compounds are linkedto one another via bridges Y¹ -Y⁴, such as --O--, --S--, --CO--O--,--O--CO--, --O--CO--O--, --CO--NR--, --NR--CO--, --O--CO--NR--,--NR--CO--O--, --NR--CO--NR--, or alternatively via a direct bond, whereat least one link of the spacer A¹ or A² to the mesogenic group is via acarbonate group (--OCOO--), a carbamate group (--O--CO--NR-- or--NR--CO--O--) or a urea group (--NR--CO--NR--). Chiral polymerizablecompounds containing one of these groups have the advantageous propertyof particularly low phase-transition temperatures and broad phase rangesand are thus particularly suitable for applications at room temperature.This is particularly true of the carbonate group.

Suitable spacers A¹ and A² are all groups known for this purpose. Thespacers generally contain from 2 to 30, preferably 3 to 12, carbon atomsand comprise predominantly linear aliphatic groups. They can beinterrupted in the chain by, for example, nonadjacent oxygen or sulfuratoms or imino or alkylimino groups, such as methylimino groups.Suitable substituents for the spacer chain are furthermore fluorine,chlorine, bromine, cyano, methyl and ethyl.

Examples of representative spacers are the following:

--(CH₂)_(p) --, --(CH₂ CH₂ O)_(m) CH₂ CH₂ --, --CH₂ CH₂ SCH₂ CH₂ --,--CH₂ CH₂ NHCH₂ CH₂ --, ##STR3## where m is from 1 to 3, and p is from 1to 12.

The radicals M can be any known mesogenic groups. Particularly suitablegroups are those of the formula Ia

    --(--T--Y.sup.5 --).sub.r --T--                            Ia

where

T is a divalent saturated or unsaturated iso- or heterocyclic radical,

Y⁵ is a bridge as defined for Y¹ -Y⁴ ; --CH₂ --O--; --O--CH₂ --;--CH═N--, --N═CH-- or --N═N--,

r is 0, 1, 2 or 3, where the radicals T and Y⁵, in the case where ris >0, may be identical or different.

r is preferably 1 or 2.

The radicals T can also be ring systems substituted by fluorine,chlorine, bromine, cyano, hydroxyl or nitro. Preferred radicals T arethe following: ##STR4##

Examples of preferred mesogenic groups M are the following: ##STR5##

Particular preference is given to mesogenic groups M of the followingformulae ##STR6## where each ring can carry up to three identical ordifferent substituents from the following group:

C₁ -C₂₀ -alkyl, C₁ -C₂₀ -alkoxy, C₁ -C₂₀ -alkoxycarbonyl, C₁ -C₂₀-monoalkylaminocarbonyl, C₁ -C₂₀ -alkylcarbonyl, C₁ -C₂₀-alkylcarbonyloxy, C₁ -C₂₀ -alkylcarbonylamino, formyl, halogen, cyano,hydroxyl or nitro.

Besides fluorine, chlorine, bromine, cyano, formyl and hydroxyl,preferred substituents for the aromatic rings are in particularshort-chain aliphatic radicals, such as methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, tert-butyl and alkoxy, alkoxy-carbonyl,alkylcarbonyl, alkylcarbonyloxy, alkylcarbonylamino andmonoalkylaminocarbonyl radicals containing these alkyl groups.

The outer benzene rings in the particularly preferred groups Mpreferably have the following substitution patterns: ##STR7## or aresubstituted analogously by F, Br, CH₃, OCH₃, CHO, COCH₃, OCOCH₃ or CNinstead of Cl, it also being possible for the substituents to be mixed.Mention should also be made of the structures ##STR8## where s is from 2to 20, preferably from 8 to 15.

The preferred substitution patterns of the central benzene ring in theparticularly preferred groups M are the following: ##STR9##

Preferred novel compounds I are also those in which the radical pairs Z¹and z², Y¹ and Y², Y³ and Y⁴ and A¹ and A² are in each case identical.

For industrial applications, especially in the printing sector, it isoften important to adjust to a required viscosity.

It is therefore also possible for this purpose to prepare mixtures ofthe novel compounds I. Such mixtures usually have a lower viscosity thanthe pure components of the mixture and generally have lowerliquid-crystalline phase temperatures so that, in some cases, they aresuitable for applications at room temperature.

The molecule fragments occurring in the mixtures of the novel compoundsmay be not only, for example, "trinuclear", and unsubstituted orring-substituted mesogenic groups M of the formula ##STR10## where informula Ia Y⁵ is ##STR11## T is three identical radicals ##STR12## (forthe unsubstituted case), r is 2,

but also, for example, "binuclear ring" groups M of the formulae##STR13## where in formula Ia Y⁵ is a single chemical bond,

T is different radicals ##STR14## (unsaturated isocyclic) and ##STR15##(saturated heterocyclic), r is 1, or ##STR16## where in formula Ia Y⁵ isa single chemical bond,

T is different radicals ##STR17## (unsaturated isocyclic) and ##STR18##(unsaturated heterocyclic), r is 1.

Particularly preferred "binuclear" mesogenic groups M in this connectionare the fragments ##STR19## which may additionally be substituted on thearomatic rings as described above.

Also claimed according to the invention are liquid-crystal compositionswhich, besides compounds I, may comprise one or more compounds of theformula II

    Z.sup.3 --Y.sup.6 --A.sup.3 --Y.sup.7 --M--Y.sup.8 --P.sup.1II,

where

Z³ are radicals containing reactive groups via which polymerization canbe effected,

Y⁶ -Y⁸ are a single chemical bond, oxygen, sulfur, --O--CO--, --CO--O--,--O--CO--O--, --CO--NR--, --NR--CO--, --O--CO--NR--, --NR--CO--O-- or--NR--CO--NR--, where at least one of the groups Y⁷ and Y⁸ is--O--CO--O--, --O--CO--NR--, --NR--CO--O or --NR--CO--NR--,

A³ is a spacer having 2 to 30 carbon atoms in which the carbon chain maybe interrupted by ether oxygen, thioether sulfur or by nonadjacent iminoor C₁ -C₄ -alkylimino groups,

P¹ are radicals selected from the group of hydrogen, C₁ -C₃₀ -alkyl, C₁-C₃₀ -acyl, C₃ -C₈ -cycloalkyl unsubstituted or substituted by one tothree C₁ -C₆ -alkyl and where the carbon chain of the alkyl, acyl andcycloalkyl radicals may be interrupted by ether oxygen, thioether sulfuror by nonadjacent imino or C₁ -C₄ -alkylimino groups. ##STR20##

It is further possible to add one or more compounds of the formula III

    P.sup.2 --Y.sup.9 --M--Y.sup.10 --P.sup.3                  III,

where

P²,P³ are radicals selected from the group of hydrogen, C₁ -C₃₀ -alkyl,C₁ -C₃₀ -acyl, C₃ -C₈ -cycloalkyl unsubstituted or substituted by one tothree C₁ -C₆ -alkyl, and where the carbon chain of the alkyl, acyl andcycloalkyl radicals may be interrupted by ether oxygen, thioether sulfuror by nonadjacent imino or C₁ -C₄ -alkylimino groups,

Y⁹, Y¹⁰ are a single chemical bond, oxygen, sulfur, --O--CO--,--CO--O--, --O--CO--O--, --CO--NR--, --NR--CO--, --O--CO--NR--,--NR--CO--O-- or --NR--CO--NR--, where at least one of the groups Y⁹ andY¹⁰ is --O--CO--O--, --O--CO--NR--, --NR--CO--O or --NR--CO--NR--,

M is a mesogenic group.

These would be, for example, compounds such as ##STR21## but also othercompounds of the formula III, some of which are commercially available.

If the novel liquid-crystal compositions which, besides compounds of theformula I as components, also comprise compounds of the formulae II andIII as components b) and c) respectively are polymerized, there is,owing to the addition of the latter two compounds, a reduction in thedensity of crosslinking of the resulting polymer. This makes it possibleto adjust properties such as hardness, elasticity, glass transitiontemperature, permeability to liquids and gases etc. of the resultingpolymerized products.

Liquid-crystal compositions which comprise one or more of compounds I,II and III may additionally comprise one or more chiral compounds. Thisresults in cholesteric liquid-crystalline phases which have, inparticular, interesting optical properties and, for example, reflectlight of different wavelengths depending on the observation angle.Liquid-crystal compositions of this type are used, in particular, ascholesteric liquid-crystalline colorants.

Particularly suitable chiral components are those which, on the onehand, have a high twisting power and, on the other hand, are readilymiscible with the liquid-crystalline compounds without adverselyaffecting the liquid-crystalline phase structure.

Examples of preferred chiral compounds are those of the formulae Ib, Ic,Id, Ie

    (Z.sup.1 --Y.sup.5).sub.n X                                Ib,

    (Z.sup.1 --Y.sup.1 --A.sup.1 --Y.sup.5).sub.n X            Ic,

    (P.sup.1 --Y.sup.5).sub.n X Id

    (Z.sup.1 --Y.sup.1 --A.sup.1 --Y.sup.3 --M--Y.sup.4).sub.n XIe,

where the variables have the meanings stated for formulae I, Ia and II,n is a number from 1 to 6, and X is an n-valent chiral radical.

Examples of radicals X are: ##STR22## where L is C₁ -C₄ -alkyl, C₁ -C₄-alkoxy, halogen, COOR, OCOR, CONHR or NHCOR, and R is C₁ -C₄ -alkyl.

(The terminal dashes in the above formulae indicate the free valencies.)

Particular preference is given, for example, to ##STR23##

These and other preferred chiral components are mentioned, for example,in DE-A 43 42 280 and the earlier German Patent Applications 19520660.6and 19520704.1.

Components a), b) and c) are preferably employed in the liquid-crystalcompositions in molar proportions, based on the total amount of saidcomponents, of

a) 1-98 mol %,

b) 1-98 mol %,

c) 0.01-90 mol %,

where the total of the individual molar proportions must, of course, be100 mol %.

If liquid-crystal compositions which, besides components a), b) and c),also contain one or more chiral compounds, are used it is preferred forthe former components to be mixed in a proportion of from 60 to 99.999%by weight with the latter chiral compounds in a proportion of from 0.001to 40% by weight, once again the proportions by weight being based onthe total of the proportions of components a), b) and c) plus chiralcompounds. The total of the proportions is, of course, once again 100%by weight.

Further novel liquid-crystal compositions contain 10-100% by weight,preferably 50-100% by weight, particularly preferably 60-100% by weight,of compounds I, I and II and/or III, in each case based on the totalweight of the liquid-crystal composition. In addition, the mixtures maycontain 0-90% by weight, preferably 0-50% by weight, of other monomerslike the crosslinkers described hereinafter, and 0-50% by weight,preferably 0-10% by weight, of one or more polymerizable ornonpolymerizable chiral compounds.

It is possible by polymerizing the novel compounds or liquid-crystalcompositions to fix the liquid-crystalline ordered state. Thepolymerization can take place, for example, thermally or photochemicallydepending on the polymerizable group. It is also possible tocopolymerize other monomers with the novel compounds or liquid-crystalcompositions. These monomers can be other polymerizableliquid-crystalline compounds, chiral compounds, which are likewisepreferably copolymerized covalently, or conventional crosslinkers suchas polyvalent acrylates, vinyl compounds or epoxides. In the particularcase of isocyanates, isothiocyanates or epoxides as polymerizableliquid-crystalline compounds, the crosslinker is preferably a polyhydricalcohol so that, for example, urethanes can be formed. The amount ofcrosslinker must be matched to the polymerization conditions so that, onthe one hand, satisfactory mechanical stability is achieved but, on theother hand, the liquid-crystalline phase behavior is not impaired. Theamount of crosslinker therefore depends on the use of the polymers. Forthe preparation of pigments, a relatively large amount of crosslinker isadvantageous, while the preparation of thermoplastic layers or, forexample, for display alignment layers requires a relatively small amountof crosslinker. The amount of crosslinker can be determined by a fewpreliminary experiments.

A further modification of the polymerized products prepared from thenovel compounds or liquid-crystal compositions is possible by addingpolymeric auxiliaries before the polymerization. Auxiliaries of thistype should preferably be soluble either in the initial mixtures or elsein an organic solvent compatible with the initial mixtures. Typicalrepresentatives of such polymeric auxiliaries are, for example,polyesters, cellulose esters, polyurethanes and polyether- orpolyester-modified or else unmodified silicones. The amount of polymericauxiliary to be added where appropriate for the required purpose, itschemical nature and possibly also the amount and nature of a solvent aregenerally familiar to the skilled worker or can likewise be determinedby a few preliminary experiments.

Besides the compounds of the formulae II (component b) and III(component c), it is also possible to admix with the polymerizableliquid-crysalline compounds of the formula I (component a) othercompounds which are incorporated noncovalently into the polymericnetwork. Possible examples of these are commercially obtainable nematicliquid crystals.

Further additives may also be pigments, dyes and fillers.

With regard to pigments, these can be inorganic compounds such as ironoxides, titanium oxide and carbon black, organic compounds, for examplepigments or dyes from the classes of monoazo pigments, monoazo dyes andtheir metal salts, disazo pigments, condensed disazo pigments,isoindoline derivatives, derivatives of naphthalene- orperylenetetracarboxylic acid, anthraquinone pigments, thioindigoderivatives, azomethine derivatives, quinacridones, dioxazines,pyrazoloquinazolones, phthalocyanine pigments or basic dyes such astriarylmethane dyes and their salts.

Further suitable pigments are those which confer an effect, such asaluminum or mica flakes or else pigments such as the pearlescent andeffect pigments commercially obtainable under the names Iriodin® andPaliocrom®.

It is furthermore possible to add conventional fillers such as chalk,talc, gipsum, barytes, etc.

The novel compounds are prepared by methods known per se. In general,the moieties Z¹, Z², A¹, A² and M are linked to one another bycondensation reactions in such a way that the bridges Y¹ to Y⁴ areformed. The starting components here are selected so that thecorresponding esters or amides are formed. This reaction principle alsoapplies to the synthesis of the mesogenic group from the correspondingring system components. The carbonate group is preferably formed bysuccessive reaction of hydroxyl-carrying moieties with phosgene.Carbamate groups and urea groups are formed correspondingly fromphosgene and amino compounds.

A preferred synthetic route for compounds of the formula I where thevariables Y³ and Y⁴ are both --O--CO--O starts with reaction of a Z¹--CO--Cl acid chloride with a spacer diol with formation of an estergroup as Y¹ : ##STR24##

The resulting hydroxyl compound can then be reacted with a compoundCl--OC--M--CO--Cl or, preferably, first with one equivalent of phosgenein accordance with the following reaction ##STR25## to form thecorresponding chloroformate, and subsequently with a mesogen diol togive the target compound: ##STR26##

In this case, a symmetrical compound in which Z¹ --Y¹ --A¹ --Y³ -- isidentical to --Y⁴ --A² --Y² --Z² is formed. It is also possible in sucha one-step reaction to react several different chloroformates as mixtureor spatially separate, successively or simultaneously, with the mesogendiol or a mixture of mesogen diols. However, this results in mixtures ofsymmetrical and asymmetrical liquid-crystalline compounds. Asymmetricalcompounds can be obtained deliberately by stepwise reaction with oneequivalent of the mesogen diol followed by reaction with a compoundCl--CO--O--A² --Y² --Z².

The procedure for this is advantageously to deviate from thestoichiometric molar ratio of 1:2 for mesogen diol: (Z¹ --Y¹ --A¹--O--CO--Cl+Z² --Y² --A² --O--CO--Cl) and to introduce the diol in amolar excess of from 5:2 to 20:2, preferably 10:2, in a solvent. Thechloroformate Z¹ --Y¹ --A¹ --O--CO--Cl is added, and the excess,unreacted mesogen diol is precipitated with a precipitant. After thesolid has been filtered off, in a second step the chloroformate Z² --Y²--A² --O--CO--Cl is added to the filtrate which contains theintermediate Z¹ --Y¹ --A¹ --O--CO--O--M--OH which is readily soluble inboth the solvent and the precipitant. A conventional workup results inthe pure mixed compound Z¹ --Y¹ --A¹ --Y³ --M--Y⁴ --A² --Y² --Z² or, inthe case of an asymmetrical mesogenic group M or on use of a pluralityof mesogen diols, a corresponding mixture of isomers or a mixture ofasymmetrical compounds I.

Examples of solvents which can generally be employed for this aredimethylacetamide, N-methylpyrrolidone, dimethylformamide, methyl ethylketone or acetone, and of precipitants are methanol, ethyl acetate,dichloromethane or butyl acetate, the action as solvent or precipitantbeing, of course, dependent on the dissolving properties of the mesogendiols and, moreover, it being necessary for the intermediate to bereadily soluble in the mixture of solvent and precipitant. For theexample of the mesogen diol 1,4-bis(4-hydroxybenzoyloxy)-2-methylbenzene##STR27## the combination of dimethylformamide and ethyl acetate assolvent and precipitant, respectively, is very suitable.

It is further advantageous, for trapping of the HCl produced, to add abase in an amount which is at least equimolar to the amount ofchloroformate before each chloroformate addition step. Suitable for thispurpose are tertiary amines such as trimethyl-, triethyl- or elseN,N-dimethylcyclohexylamine, pyridine or else inorganic bases such asalkali metal or alkaline earth metal carbonates or bicarbonates, andmixtures of organic and inorganic bases.

Further bases which can be employed are alkali metal or alkaline earthmetal acetates. It is preferred to add N,N-dimethylcyclohexylamine andpotassium carbonate, either alone or in a mixture.

The reactions are generally carried out at from 0° C. to 60° C., usuallyfrom 40° C. to 50° C. The reactions last from 3 to 24 hours, dependingon the reactivity of the reactants.

The workup usually involves diluting the reaction mixture with water andan organic extractant which is immiscible or of only low miscibilitywith water, and washing the organic phase several times with water andfinally with aqueous mineral acid.

The organic extractant is removed by distillation under reduced pressureat from 20° C. to 40° C. To prevent premature polymerization of theproduct(s), conventional inhibitors such as methoxyphenol, Kerobit® BHTor phenothiazine, usually in a mixture, in amounts of from 0.01 to 1% byweight, based on the product(s), are added before the distillation. Themixture of inhibitors differing in volatility ensures adequatestabilization of the product(s) in both the liquid and vapor phases.

Preferably used as organic extractants are toluene or ethyl acetate.Concentrated hydrochloric acid is preferably used for the acid wash.

It is possible and preferred also to add diluents for the reaction ofthe mesogen diols with the chloroformates. These reduce the viscosity ofthe reaction mixture and thus ensure faster mixing of the reactants andthus a shortening of the reaction time. Examples of advantageousdiluents which can be used are toluene, xylene, ethyl acetate, butylacetate or else tetrahydrofuran or the various isomeric dioxanes. It isfurthermore possible for the diluent itself to act as base, for examplethe abovementioned tertiary amines or else pyridine.

The novel preparation of the compounds of the formula II where thevariables Y⁷ and Y⁸ are --O--CO--O-- takes place in a similar way to thespecific stepwise preparation of the mixed compounds Z¹ --Y¹ --A¹--O--CO--O--M--O--CO--O--A² --Y² --Z². In this case, either the mesogendiol can be reacted in the first step with the chloroformate Z³ --Y⁶--A³ --O--CO--Cl and in the second step with P¹ --O--CO--Cl, or thechloroformates are added in the reverse sequence.

If it is intended to prepare a liquid-crystal composition which, besidescompound I, also comprises compounds II and III, it can be preparedprimarily by mixing the individual compounds in the abovementionedpreferred proportions.

A simple way consists of reacting one or more diols with one or morechloroformates of the formula Z¹ --Y¹ --A¹ --O--CO--Cl and with one ormore chloroformates of the formula P¹ --O--CO--Cl. In this case, thechloroformates are added either simultaneously but separately or in theform of a mixture. If particular compounds I, II and III are to beprepared specifically in above or below the stoichiometric amount, it isalso expedient to add the various chloroformates stepwise.

The preferred molar ratio of chloroformate(s) Z¹ --Y¹ --A¹ --O--CO--Clto chloroformate(s) P¹ --O--CO--Cl for preparing such liquid-crystalcompositions is from 99:1 to 20:80, preferably from 99:1 to 40:60. Aratio of 50:50 is particularly preferably chosen.

If mixtures of chloroformates are employed, and if the reactivities ofthe chloroformates are identical, both with one another and toward thediol HO--M--OH or the corresponding monohydroxy intermediate (singlysubstituted mesogen diol), it is possible to determine the (random)distribution of the compounds I, II and III in accordance with thestatements below. For simplicity, the following definitions are givennow: ##STR28##

Reaction of the diol(s) with a mixture of chloroformates in the molarratio of ##STR29## of 99:1 results, in the ideal case, in the followingdistribution after the first substitution ##STR30##

Each of these intermediates in turn undergoes second substitution in theabove ratio of 99:1, ie. ##STR31##

If the two products with mixed substituents are identical, ie. if themesogen diol is symmetrical, the resulting ratio of compounds I to II toIII is 98.01%:1.98% (=2×0.99%):0.01%.

Similarly, for a corresponding chloroformate mixture in the molar ratio20:80 or 40:60 or 50:50, the resulting molar ratio of compounds I, IIand III is 4%:32% (=2×16%):64% or 16:48% (=2×24%):36% or 25%:50%(=2×25%):25%.

It is possible to form the various other groups Y¹ -Y⁴ in a similar way,preferably reacting acid halides with the appropriate amino or hydroxylcompounds. Oxygen and sulfur bridges are introduced into the compoundsin a known manner by ether synthesis methods.

Further details of the preparations of the compounds are given in WO95/22586, WO 95/24454 and WO 95/24455.

The novel liquid-crystal compositions are outstandingly suitable forcoating surfaces. A process for the production of such coatings having aliquid-crystalline ordered state comprises diluting the novelliquid-crystal compositions, which may comprise further polymerizablecompounds and chiral compounds, if desired with a diluent to reduce theviscosity, applying the mixture to a substrate, effecting aliquid-crystalline alignment and then polymerizing the compounds appliedto the substrate.

The liquid-crystalline alignment is formed either spontaneously duringapplication or is achieved by known physical methods, for examplerubbing or application of an electric or magnetic field.

If, for example, it is intended to use the novel liquid-crystalcomposition in the screen printing sector, the viscosity thereof can bereduced not only by said addition of diluents or by using mixtures ofnovel compounds I and II but also through the proportions ofnoncrosslinking compound III. By contrast with this, higher viscositiescan be tolerated or are even desired for example in the automotivepaints sector.

The novel compounds or liquid-crystal compositions are used, forexample, for producing optical display devices, in particular forproducing alignment layers in liquid-crystal displays. The compounds orcompositions can also be used as polymerizable matrix components forpolymer-dispersed displays.

Further possible uses are photocrosslinkable adhesives based on liquidcrystals.

The novel compounds or liquid-crystal compositions are particularlypreferably used in cholesteric liquid-crystalline mixtures which areused as liquid-crystalline colorants. Particular mention should be madein this context of automotive paints based on cholesteric liquid-crystalsystems. These paints can either be produced by direct coating of thesubstrates or may contain pigments which comprise the novel compounds ina cholesteric liquid-crystalline ordered state fixed by polymerization.

The novel liquid-crystal compositions can also be used to producepigments. This involves polymerization of the liquid-crystal compositionand comminuting and grading the resulting polymer using conventionalunits. This preferably involves the initial composition being applied asa thin layer with a knife and, if desired, being additionally aligned inan electric or magnetic field. Pigments in platelet form are alsoobtainable in this way.

EXAMPLES

    ______________________________________                                        Explanation of symbols:                                                       ______________________________________                                        n.d.      not determined                                                                              cr       crystalline                                    s smectic i isotropic                                                         n nematic ch cholesteric                                                    ______________________________________                                    

The following notation is used to characterize the phase behavior:

Example a): cr 78-83 n 87-88 i means that the crystalline phase (cr) iscoexistent with the nematic phase (n) at from 78 to 83° C. The range ofcoexistence of nematic and isotropic phase (i) is from 87 to 88° C.Above 88° C. an isotropic "clarified" melt exists.

Example b): cr 77 i means that the transition from the crystalline phase(cr) to an isotropic phase (i) = melt takes place at 77° C.

The phase behavior of the compounds or mixtures was investigated bypolarized-light microscopy. The temperature was controlled by means of aMettler FP 80/82 type heated stage.

Viscosities were determined with a Rheometrics dynamic spectrometer(supplied by Rheometrics) with cone/plate geometry.

Coatings were prepared from some mixtures using a flat knife and wereassessed either visually or by means of a spectrometer (Hitachi U-2000supplied by Hitachi). On visual assessment, the meaning of, for example,"red-green" is that the coating showed a red color when viewedperpendicularly and showed a green color hen viewed at a small angle.The measured wavelengths λ(⊥) relate to the reflected light viewedperpendicularly.

Preparations

Preparation Method 1

Preparation of the compounds (Examples 1 to 14) ##STR32##

A solution of 12 mmol of a chloroformate ##STR33## in 5 ml ofdichloromethane was added dropwise to a solution of 5 mmol of1,4-bis(4-hydroxybenzoyloxy)-2-R¹ -benzene (mesogen diol) 20 ml ofpyridine at 0° C., after which the reaction mixture was stirred at roomtemperature for 3 hours. Dilute hydrochloric acid was then added,whereupon the product precipitated as a solid, and it was filtered off,washed and purified by recrystallization.

The details of these experiments and the results thereof are to be foundin Table 1 below.

                  TABLE 1                                                         ______________________________________                                        Ex.   R.sup.1                                                                              R.sup.2                                                                              n    Liquid-crystalline temperature range [°                                C.]                                                  ______________________________________                                        1     H      H      2    124-162                                                2 H H 4  71->100 (polymerized)                                                3 H H 6 n.d.                                                                  4 H H 8  69-136                                                               5 CH.sub.3 H 2 117-166                                                        6 CH.sub.3 H 4  58-119                                                        7 CH.sub.3 H 6  53-110                                                        8 CH.sub.3 H 8  46-80                                                         9 Cl H 2  80-120                                                              10  Cl H 4 <20-95                                                             11  Cl H 6 <20-51                                                             12  Cl H 8  45-100                                                            13  H CH.sub.3 2 155-169                                                      14  H CH.sub.3 4 103->130 (polymerized)                                     ______________________________________                                    

Preparation Method 2

As) Preparation of the compound (Example 15) ##STR34## 95.1 g (0.25 mol)of 1-(3-methoxy-4-hydroxybenzoyloxy)-4-(4-hydroxybenzoyloxy)benzene weredissolved in 182 ml of dimethylformamide and 95.25 g (0.75 mol) ofdimethylcyclohexylamine and, at room temperature, 124.96 g (0.605 mol)of acryloyloxybutyl chloroformate were added dropwise over the course of30 minutes. The mixture was then stirred at 40° C. for 3.5 h and at roomtemperature overnight. Addition of water was followed by dilution withethyl acetate, adjustment to pH 1 with concentrated hydrochloric acid,removal of the aqueous phase and washing of the organic phase with watertwice. After the organic phase had been dried, the ethyl acetate wasremoved under reduced pressure, and the crude product was purified byfiltration through silica gel with the eluent petroleum ether/ethylacetate 2:1. The product showed the following phase behavior:

cr 78-83 n 87-88 i

Ab) Preparation of the compound (Example 16) ##STR35## 96.1 g (0.25 mol)of the compound ##STR36## were dissolved in 182 ml of dimethylformamideand 47.6 g (0.375 mol) of dimethylcyclohexylamine and, at roomtemperature, 62.5 g (0.303 mol) of acryloyloxybutyl chloroformate wereadded dropwise over the course of 30 minutes. The mixture was thenstirred at 40° C. for 3.5 h and at room temperature overnight. Additionof water was followed by dilution with ethyl acetate, adjustment to pH 1with concentrated hydrochloric acid, removal of the aqueous phase andwashing of the organic phase with water twice. After the organic phasehad been dried, the ethyl acetate was removed under reduced pressure,and the crude product was purified by filtration through silica gel withthe eluent petroleum ether/ethyl acetate 2:1. A pure product wasobtained as oil.

Ac) Preparation of the compounds (Examples 17 to 22) ##STR37## 57.5 g(0.25 mol) of 4-(4-hydroxybenzoyloxy)phenol were dissolved in 182 ml ofdimethylformamide and 95.25 g (0.75 mol) of dimethylcyclohexylamine and,at room temperature, 0.605 mol of the chloroformate ##STR38## was addeddropwise over the course of 30 minutes. The mixture was then stirred at40° C. for 3.5 h and at room temperature overnight. Addition of waterwas followed by dilution with ethyl acetate, adjustment to pH 1 withconcentrated hydrochloric acid, removal of the aqueous phase and washingof the organic phase with water twice. After the organic phase had beendried, the ethyl acetate was removed under reduced pressure, and thecrude product was purified by filtration through silica gel with theeluent petroleum ether/ethyl acetate 2:1.

The details of the experiments are to be found in Table 2 below.

                  TABLE 2                                                         ______________________________________                                        Ex.        R         n     Phase behavior                                     ______________________________________                                        17         H         2     n.d.                                                 18 H 4 cr 41 i                                                                19 H 6 n.d.                                                                   20 CH.sub.3 2 n.d.                                                            21 CH.sub.3 4 n.d.                                                            22 CH.sub.3 6 n.d.                                                          ______________________________________                                    

Ba) Preparation of the compounds (Examples 23 to 27) ##STR39## 0.25 molof the compound ##STR40## was dissolved in 182 ml of dimethylformamideand 47.6 g (0.375 mol) of dimethylcyclohexylamine and, at roomtemperature, 0.303 mol of the chloroformate ##STR41## was added dropwiseover the course of 30 minutes. The mixture was then stirred at 40° C.for 3.5 h and at room temperature overnight. Addition of water wasfollowed by dilution with ethyl acetate, adjustment to pH 1 withconcentrated hydrochloric acid, removal of the aqueous phase and washingof the organic phase with water twice. After the organic phase had beendried, the ethyl acetate was removed under reduced pressure, and thecrude product was purified by filtration through silica gel with theeluent petroleum ether/ethyl acetate 2:1.

The details of the experiments are to be found in Table 3 below.

                  TABLE 3                                                         ______________________________________                                        Ex.    R               n        Phase behavior                                ______________________________________                                        23     OCH.sub.3       4        cr 51 i                                         24 CH.sub.3 4 cr 39 i                                                         25 C.sub.8 H.sub.17 2 oil                                                     26 C.sub.8 H.sub.17 4 oil                                                     27 C.sub.9 H.sub.19 4 oil                                                     28 COCH.sub.3 4 cr 77 i                                                       29 COC.sub.2 H.sub.5 4 cr 59 n 68 i                                           30 COC.sub.4 H.sub.9 4 cr 50-52 n                                                58-59 i                                                                    31 COOC.sub.2 H.sub.5 2 n.d.                                                  32 COOC.sub.2 H.sub.5 4 cr 48 i                                               33 COOC.sub.4 H.sub.9 4 cr 30-32 i                                            34 COOC.sub.6 H.sub.13 4 cr 39-40 i                                           35 COOC.sub.8 H.sub.17 4 cr 38-40 i                                            - 36                                                                                                         4 cr 86 i                                      - 37                                                                                                         4 cr 60-62 i                                ______________________________________                                    

Bb) Preparation of the compounds (Examples 38 to 40) ##STR44## 0.25 molof the compound ##STR45## was dissolved in 182 ml of dimethylformamideand 47.6 g (0.375 mol) of dimethylcyclohexylamine and, at roomtemperature, 62.5 g (0.303 mol) of acryloyloxybutyl chloroformate wereadded dropwise over the course of 30 minutes. The mixture was thenstirred at 40° C. for 3.5 h and at room temperature overnight. Additionof water was followed by dilution with ethyl acetate, adjustment to pH 1with concentrated hydrochloric acid, removal of the aqueous phase andwashing of the organic phase with water twice. After the organic phasehad been dried, the ethyl acetate was removed under reduced pressure,and the crude product was purified by filtration through silica gel withthe eluent petroleum ether/ethyl acetate 2:1.

The details of the experiments are to be found in Table 4 below.

                  TABLE 4                                                         ______________________________________                                        Ex.      R               Phase behavior                                       ______________________________________                                        38       OCH.sub.3       oil                                                     - 39                                                                                                  oil 46##                                              - 40                                                                                                  oilR47##                                           ______________________________________                                    

Preparation Method 3

Preparation of the compound (Example 6) ##STR48##

364 g (1.0 mol) of 1,4-bis(4-hydroxybenzoyloxy)-2-methylbenzene and303.5 g (2.2 mol) of potassium carbonate were suspended in 1 liter ofN-methylpyrrolidone and, at room temperature, 495.6 g (2.4 mol) ofacryloyloxybutyl chloroformate were added over the course of 30 minutes.The mixture was stirred at 40° C. for 30 minutes and then 151.0 g (1mol) of dimethylcyclohexylamine were added, and the mixture was stirredat 40° C. for a further 3 h. Then 2 liters of toluene were added and themixture was extracted by stirring twice with 2 liters of water eachtime. After the aqueous phase had drained off, 2 liters of water wereadded and the pH was adjusted to 1 with 128 g of concentratedhydrochloric acid. A further two extractions by 2 liters of water eachtime were then carried out. After removal of the aqueous phase, 85 mg ofKerobit BHT and 85 mg of methoxyphenol were added and the toluene wasevaporated off under reduced pressure at a maximum bath temperature of40° C. The crude yield was 730.6 g. Filtration through silica gel withpetroleum ether/ethyl acetate as eluent resulted in 678.7 g (96%) of1,4-bis(4-acryloyloxybutoxycarbonyloxybenzoyloxy)-2-methylbenzene (phasebehavior: cr 58 n 122 i).

Preparation Method 4

A) Selective preparation of asymmetrical compounds (Examples 41 and 42)##STR49## 23 g (0.1 mol) of 4-(4-hydroxybenzoyloxy)phenol were dissolvedin 100 g of dimethylformamide, and 1.2 g (0.01 mol) ofdimethylcyclohexylamine were added. Then 0.01 mol of the chloroformate##STR50## was added at room temperature. The mixture was stirred at 40°C. for 4 h and then 200 ml of ethyl acetate were added. The precipitatedsolid (excess 4-(4-hydroxybenzoyloxy)phenol) was filtered off withsuction, and the filtrate was heated to 80° C. After about 180 ml ofethyl acetate had been distilled off, 0.01 mol of the chloroformate##STR51## and a further 1.2 g (0.01 mol) of dimethylcyclohexylamine wereadded to the mother liquor, which was then stirred at 40° C. for 4 h.The reaction mixture was poured into 200 ml of water and extracted threetimes with 100 ml of ethyl acetate each time. The combined organicphases were dried over sodium sulfate and, after removal of the solvent,the crude product was purified by chromatography to result in a mixtureof the two isomeric diacrylates ##STR52##

Table 5 contains details of the experiments.

                  TABLE 5                                                         ______________________________________                                        Ex.     n            m     Phase behavior                                     ______________________________________                                        41      2            4     n.d.                                                 42 4 6 n.d.                                                                 ______________________________________                                    

B) Selective preparation of the asymmetrical compound (Example 43)##STR53## 36.4 g (0.1 mol) of1,4-bis(4-hydroxybenzoyloxy)-2-methylbenzene were dissolved in 100 g ofdimethylformamide, and 1.2 g (0.01 mol) of dimethylcyclohexylamine wereadded. Then 2.08 g (0.01 mol) of acryloyloxybutyl chloroformate wereadded at 15 to 20° C. The mixture was stirred at 40° C. for 4 h and then200 ml of ethyl acetate were added. The precipitated solid was filteredoff with suction, and the filtrate was heated to 80° C. After about 180ml of ethyl acetate had been distilled off, 1.36 g (0.01 mol) of butylchloroformate and a further 1.2 g (0.01 mol) of dimethylcyclohexylaminewere added to the mother liquor, which was then stirred at 40° C. for 4h. The reaction mixture was poured into 200 ml of water and extractedthree times with 100 ml of ethyl acetate each time. The combined organicphases were dried over sodium sulfate and, after removal of the solvent,the crude product was purified by chromatography to result in 5.72 g(90%) of the two isomeric monoacrylates ##STR54## Phase Behavior: n 134i Preparation Method 5

Aa) Preparation of random mixtures of compounds (Examples 44 to 46)##STR55## 350 g (1.0 mol) of 1,4-bis(4-hydroxybenzoyloxy)benzene wereintroduced into 728 ml of dimethylformamide, and 381 g (3 mol) ofdimethylcyclohexylamine were added. Between 0° C. and 5° C., a mixtureof 2.1 mol of acryloyloxybutyl chloroformate (chloroformate CF1) and2-acryloyloxy-2-methylethyl chloroformate/2-acryloyloxy-1-methylethylchloroformate (chloroformate CF2; a mixture of the two isomericcompounds results from the preparation of the chloroformate, but therelative proportions of the 2- and 1-methyl compounds could not bedetermined) in the molar ratio of the butyl compound to the mixture ofthe isomeric methyl ethyl compounds of 70:30 or 80:20 or 90:10 was addeddropwise over the course of 30 minutes. The reaction mixture was thenstirred at 40° C. for 3 h.

The mixture was diluted with 2 liters of toluene and 1 liter of waterand acidified with 120 ml of concentrated hydrochloric acid. Drainingoff the aqueous phase was followed by washing to neutrality with 2×500ml of water. After addition of 63.5 mg of Kerobit® BHT, 63.5 mg ofmethoxyphenol and 126.8 mg of phenothiazine to the organic phase, thetoluene was removed by distillation under reduced pressure at a bathtemperature of 40° C.

The results of the experiments are compiled in Table 6 below.

                  TABLE 6                                                         ______________________________________                                        Ex.   Molar ratio CF1*):CF2**)                                                                          Phase behavior                                      ______________________________________                                        44    70:30               s 47 n 127-131 i                                      45 80:20 s 54 n 145 i                                                         46 90:10 s 56-57 n 155-156 i                                                ______________________________________                                         ##STR56##                                                                     ##STR57##                                                                

Ab) As in Aa), a random mixture of compounds (Example 47) ##STR58## wasobtained by reacting 1.0 mol of 1,4bis(4hydroxybenzoyloxy)benzene wit2.1 mol of a 1:1 mixture of the chloroformate ##STR59##

The mixture of chloroformates can be prepared by reacting the diol##STR60## with one equivalent each of acryloyl chloride and phosgene.

The resulting mixture of the abovementioned compounds was not analyzed,bu the contents of the two symmetrical compounds ##STR61## and of theasymmetrical compound ##STR62## are expected to be in the molar ratio of(approximately) 25:25:50.

B) Preparation of random mixtures of compounds (Examples 48 and 49)##STR63## 364 g (1.0 mol) of 1,4bis(4hydroxybenzoyloxy)benzene wereintroduced into 728 ml of dimethylformamide, and 381 g (3 mol) ofdimethylcyclohexylamine were added. Between 0° C. and 5° C., a mixtureof 2.1 mol o acryloyloxybutyl chloroformate (chloroformate CF1) andbutyl chloroformat (chloroformate CF3) in the molar ratio of 50:50 or90:10 was added dropwise over the course of 30 minutes. The reactionsolution was then stirred at 40° C. for 3 h.

The mixture was diluted with 2 liters of toluene and 1 liter of waterand acidified with 120 ml of concentrated hydrochloric acid. Drainingoff the aqueous phase was followed by washing to neutrality with 2×500ml o water. After addition of 63.5 mg of Kerobit® BHT, 63.5 mg ofmethoxyphenol and 126.8 mg of phenothiazine to the organic phase, thetoluene was removed by distillation under reduced pressure at a bathtemperature of 40° C.

The results of the experiments are summarized in Table 7 below.

                  TABLE 7                                                         ______________________________________                                        Ex.   Molar ratio CF1*):CF3**)                                                                          Phase behavior                                      ______________________________________                                        48    50:50               cr 40-48 n 150-152 i                                  49 90:10 cr 38-48 n 109-113 i                                               ______________________________________                                         ##STR64##                                                                     ##STR65##                                                                

The mixtures of Examples 48 and 49 were analyzed by chromatography. Thisresulted in the mole percentages of the individual components of themixtures which were listed in Table 8. a) (corresponds to a novelcompoun of the formula I) ##STR66## b) (corresponds to a novel compoundof the formula II) ##STR67## c) (corresponds to a compound of theformula III) ##STR68##

For comparison, Table 8 also lists the mole percentages calculated forcomponents a, b and c which can be derived from the molar ratios of thechloroformates CF1 and CF3 employed.

                  TABLE 8                                                         ______________________________________                                        Component                                                                       (mol %) Example 48 Example 49                                               ______________________________________                                        a      determined  28        78                                                  calculated 25 81                                                             b determined 48 20                                                             calculated 50 (2 · 25) 18 (2 · 9)                          c determined 24  2                                                             calculated 25  2                                                           ______________________________________                                    

Mixtures:

The numbers in the following tables refer to percent by weight of helisted components of the mixtures.

A column heading "Ex. 6" or "Ex. 49" means, for example, use of aroportion, which is specified in the appropriate column, of the productfrom Preparation Example 6 or a random mixture from preparation Example49.

The additions abbreviated to "Luc", "Irga" and "Daro" in the mixturesare commercially available photoinitiators Lucirin® TPO, Irgacure® 184and Darocure® 1173. The chemical identity of the additions listed underthe other abbreviations is as follows.

    ______________________________________                                          #STR69##                                                                      n                                                                                                           Abbreviations                                 ______________________________________                                          4                                                                                                       Bob  (##                                                                    "Benzoyloxybenzene")                                   - 6                                                                                                    Isosor  ("Isosorbide")                               - 4                                                                                                    Etgly  ("Ethylene glycol")                           - 4                                                                                                    Hexgly  ("Hexamethylene glycol"                   ______________________________________                                    

    ______________________________________                                          #STR75##                                                                    R.sup.1  R.sup.2     Abbreviation                                             ______________________________________                                        --OCH.sub.3                                                                            --C.sub.4 H.sub.9                                                                         Bumeox ("Butylmethoxy")                                     - --COOC.sub.2 H.sub.5                                                                            Vicoxet ("Vinylcarboxylethyl")                            - --COOC.sub.4 H.sub.9                                                                            Vicoxbu ("Vinylcarboxylbutyl")                            - --COOC.sub.6 H.sub.13                                                                           Vicoxhe ("Vinylcarboxylhexyl")                            - --OCH.sub.3                                                                                     Vimeox ("Vinylmethoxy")                                   - --OCH.sub.3                                                                                     Mevimeox ("Methylvinylmethoxy")                           - --COCH.sub.3                                                                                    Vicame ("Vinylcarbonylmethyl")                            - --COC.sub.2 H.sub.5                                                                             Vicaet ("Vinylcarbonylethyl")                             - --COC.sub.4 H.sub.9                                                                             Vicabu ("Vinylcarbonylbutyl")                             - --C.sub.9 H.sub.19                                                                              Vinon ("Vinylnonyl")                                   ______________________________________                                    

                  TABLE 9                                                         ______________________________________                                        Mixture                                                                              Ex. 2   Ex. 6   Ex. 18                                                                              Bob   Phase behavior                             ______________________________________                                        1      85.1                  14.9  cr 31-64 n 130-138 i                         2 68.2   31.8 cr 32-58 n 110-114 i                                            3 48.8   51.2 cr 32-42 n 89-95 i                                              4 38.0   62.0 cr 31-46 n 67-71 i                                              5 26.4   73.6 cr 32-48 n 70-74 i                                              6  85.4  14.6 cr 40-67 n 107-111 i                                            7  68.7  31.3 cr 40-54 n 91-96 i                                              8  49.3  50.7 cr 35-46 n 72-77 i                                              9 82.9  17.1  s 56-64 n 140-142 i                                             10  64.5  35.5  s 46-58 n 116-119 i                                           11  54.8  45.2  s 46-51 n 98-104 i                                            12  44.7  55.3  s 46-49 n 76-80 i                                           ______________________________________                                    

                                      TABLE 10                                    __________________________________________________________________________    Mixture                                                                           Ex. 45                                                                            Ex. 23                                                                            Ex. 30                                                                            Isosor                                                                            Bumeox                                                                            Luc                                                                              Phase behavior                                     __________________________________________________________________________    13  89.2                                                                              10.8               s 39-40 n 113-119 i                                  14 79.4 20.6     n 103-105 i                                                  15 52.4 47.6     n 52-55 i                                                    16 41.5 58.5     n 58-61 i                                                    17 29.3 70.7     n 52-55 i                                                    18 28.2 39.7 32.1    n 62-63 i                                                19 27.4 21.2 51.4    n 68-69 i                                                20 58.2    41.8  s 49-50 n 93-94 i                                            21 30.4 55.1   14.5  n 53-55 i                                                22 81.3  9.8  8.9   s 40-41 ch 85-93 i                                        23 74.5 19.3  6.2   ch 78 i                                                   24 72.9 18.9  6.1  2.1 ch 68 i                                                25 72.0 18.6  9.4   ch 69-79 i; (⊥) = 546 nm                             26 72.0 18.7  7.3  2.0 ch 75 i                                                27 71.5 18.5  10.0    ch 75-80 i                                              28 70.2 18.2  9.2  2.4 ch 60 i; (⊥) = 563 nm                             29 69.8 18.1  9.7  2.4 ch 67-73 i; (⊥) = 527 nm                          30 38.4 54.1  7.5   ch 41-46 i                                                31 37.4 52.8  7.3  2.5 ch 31 i                                                32 94.4   5.6   s 48 ch 112-118 i                                             33 92.1   5.4  2.5 s 56 ch 113-118 i                                        __________________________________________________________________________

                                      TABLE 11                                    __________________________________________________________________________    Mixture                                                                           Ex. 48                                                                            Ex. 6                                                                            Ex. 18                                                                            Ex. 23                                                                            Isosor                                                                            Irga                                                                             Luc                                                                              Toluene                                                                           Phase behavior                               __________________________________________________________________________    34  72.2   27.8                  n 116-119 i                                    35 62.6  37.4      n 98-104 i                                                 36 52.7  47.3      n 93-98 i                                                  37 42.6  57.4      n 76-81 i                                                  38 57.9  34.7  7.4    ch 84-87 i                                              39 55.7  33.3  7.1 3.9   red-greed                                            40 55.0  32.9  8.3 3.8   green-blue                                           41 86.0   14.0     n 117-123 i                                                42 69.7   30.3     n 98-102 i                                                 43 50.6   49.4     n 75-79 i                                                  44 45.2   54.8     n 70-73 i                                                  45 39.7   60.3     n 64 i                                                     46 23.5   76.5     n 43-48 i                                                  47 45.3 25.1  29.6     n 100-104 i                                            48 41.4 23.0  27.1 8.5    ch 78-87 i                                          49 46.8   45.8 7.4    ch 55-67 i                                              50 45.7   44.6 7.2  2.5  ch 47 i                                              51 45.0   44.0 7.1  2.4  ch 48 i; (⊥) = 555 nm;                                  1.5 flow viscosity: 3 Pa.s                                            52 43.3   49.2 7.5    ch 56-64 i; (⊥) = 539 nm                           53 41.8   50.6 7.6    ch 53-60 i                                              54 40.8   49.4 7.4  2.4  ch 42-51 i; (⊥) = 572 nm                      __________________________________________________________________________

                                      TABLE 12                                    __________________________________________________________________________    Mixture                                                                           Ex. 48                                                                            Ex. 23                                                                            Ex. 24                                                                            Ex. 38                                                                            Isosor                                                                            Bob                                                                              Luc                                                                              Phase behavior                                  __________________________________________________________________________    55  87.6                                                                               5.1    7.3           n 109-115 i                                       56 86.9  7.7  5.4    n 110-117 i                                              57 62.7 28.6  8.7    n 72-76 i                                                58 54.5 26.6  18.9     n 44-50 i                                              59 52.4 38.5  9.1    n 60-66 i                                                60 58.0 26.5  8.1 7.4   ch 49-55 i                                            61 44.5 43.5  4.4 7.6   ch 46-53 i                                            62 43.4 42.4  4.3 7.5  2.4 ch 35 i                                            63 82.7  17.3     n 114-119 i                                                 64 65.6  34.4     n 88-93 i                                                   65 46.2  53.8     n 59-65 i                                                   66 34.7  65.3     n 42-49 i                                                   67 98.0   2.0    n 127-132 i                                                  68 84.8   15.2     n 81-95 i                                                  69 78.2   21.8     n 65-76 i;                                                         flow viscosity: 3 Pa.s                                                70 70.6   29.4     n 41-50 i;                                                         flow viscosity: 1.3 Pa.s                                              71 84.1     15.9  cr 31-54 n 120-130 i                                        72 66.4     33.6  cr 31-61 n 100-109 i                                        73 46.0     54.0  cr 31-69 n 80-84 i                                          74 24.8     75.2  cr 50 n 67-72 i                                           __________________________________________________________________________

                                      TABLE 13                                    __________________________________________________________________________    Mixture                                                                           Ex. 49                                                                            Ex. 23                                                                            Ex. 38                                                                            Ex. 43                                                                            Isosor                                                                            Daro                                                                             Luc                                                                              Toluene                                                                           Xylene                                                                            Phase behavior                          __________________________________________________________________________    75  88.9                                                                              10.1                          n 97-99 i;                                          Flow viscosity: 9 Pa.s                                              76 70.4 29.6        n 79-83 i;                                                          Flow viscosity: 5 Pa.s                                              77 50.0 50.0        n 60-62 i;                                                          Flow viscosity: 3 Pa.s                                              78 24.3 75.7        n 36-42 i;                                                          Flow viscosity: 2 Pa.s                                              79 73.7 15.4 10.9        n 59-64 i                                            80 73.2 20.2 6.6       n 65-70 i                                              81 72.1 22.6 5.3       n 68-72 i                                              82 66.5 27.7   5.8     ch 67-72 i; red-green                                  83 65.7 27.3   7.0     ch 63-69 i; red-green                                  84 65.9 27.4   6.7     ch 65 i                                                85 64.6 26.9   9.5     ch 57 i                                                86 47.9 44.8   7.3     ch 46-54 i                                             87 63.0 26.2   6.4  2.4  2.0 ch 57 i; (⊥) = 704 nm                       88 61.2 25.5   8.0  2.4 2.9  ch 50 i; (⊥) = 533 nm;                                flow viscosity: 3 Pa.s                                              89 61.3 25.5   8.0 3.7  1.5  ch 42 i; (⊥) = 533 nm;                                flow viscosity: 3 Pa.s                                              90 60.8 25.3  3.5 8.0 2.4    ch 44 i                                        __________________________________________________________________________

                                      TABLE 14                                    __________________________________________________________________________    Mixture                                                                           Ex. 49                                                                            Ex. 24                                                                            Ex. 28                                                                            Ex. 29                                                                            Ex. 31                                                                            Ex. 32                                                                            Ex. 33                                                                            Phase behavior                                __________________________________________________________________________     91 86.7                                                                              13.3                    n 95-99 i                                        92 71.4 28.6      n 75-80 i                                                   93 52.6 47.3      n 54-76 i                                                   94 29.4 70.6      n 29-32 i                                                   95 86.2  13.8     n 106-121 i                                                 96 69.0  31.0     n 92-106 i                                                  97 49.7  50.3     cr 52 n 77-92 i                                             98 85.2   14.8    n 106-119 i                                                 99 77.6   22.4    n 99-104 i;                                                        flow viscosity: 10.6 Pa.s                                             100 68.3   31.7    n 98-112 i                                                 101 58.1   41.9    n 85-87 i;                                                         flow viscosity: 10.6 Pa.s                                             102 48.9   51.1    n 88-101 i                                                 103 37.2   62.8    n 72-75 i                                                  104 84.3    15.7   n 102-104 i                                                105 63.6    36.4   n 69-72 i                                                  106 40.7    59.3   n 34-55                                                    107 78.7     21.3  n 98-103 i                                                 108 66.6     33.4  n 79-83 i                                                  109 77.6      22.4 n 88-91 i                                                  110 59.5      40.5 n 59-63 i                                                __________________________________________________________________________

                                      TABLE 15                                    __________________________________________________________________________    Mixture                                                                           Ex. 49                                                                            Ex. 34                                                                            Ex. 35                                                                            Ex. 36                                                                            Ex. 37                                                                            Ex. 38                                                                            Ex. 38                                                                            Ex. 39                                                                            Phase behavior                            __________________________________________________________________________    111 81.2                                                                              19.8                        n 91-93 i                                   112 65.6 34.4       n 69-73 i                                                 113 40.9 59.1       n 36-38 i                                                 114 80.8  19.2      n 89-92 i                                                 115 58.3  41.2      n 55-61 i                                                 116 79.8   20.2     n 103-106 i;                                                       flow viscosity: 15.7 Pa.s                                            117 73.7   26.3     n 87-90 i;                                                         flow viscosity: 11.7 Pa.s                                            118 50.8   49.2     n 67-69 i;                                                         flow viscosity: 10.6 Pa.s                                            119 81.1    18.9    n 97-100 i                                                120 59.0    41.0    n 74-77 i                                                 121 40.4    59.6    n 53-57 i                                                 122 95.8      4.2   n 96-99 i                                                 123 75.2     24.8   n 34-43 i;                                                         flow viscosity: 1.3 Pa.s                                             124 79.1      20.9  n 68-70 i                                                 125 76.2       23.8 n 59-65 i                                               __________________________________________________________________________

                                      TABLE 16                                    __________________________________________________________________________    Mixture                                                                           Ex. 49                                                                            Etgly                                                                            Hexgly                                                                            Vicoxet                                                                           Vicoxbu                                                                            Vicoxhe                                                                           Vimeox                                                                            Phase behavior                                __________________________________________________________________________    126 82.8                                                                              17.2                    n 75-81 i                                       127 77.3  22.7     n 67-73 i                                                  128 80.0   20.0    n 109-111 i                                                129 75.0   25.0    n 91-93 i                                                  130 59.3   40.7    n 97-100 i                                                 131 57.4   42.6    n 69-72 i                                                  132 47.7   52.3    n 92-95 i                                                  133 43.6   56.4    n 56-59 i                                                  134 80.8    19.2   n 101-103 i                                                135 59.3    40.7   n 79-82 i                                                  136 38.0    62.0   n 56-58 i                                                  137 79.5     20.5  n 99-101 i                                                 138 59.9     40.1  n 68-71 i                                                  139 89.4      10.6 n 112-115 i                                                140 76.0      24.0 n 108-119 i                                                141 58.4      41.6 cr 57 n 105-117 i                                        __________________________________________________________________________

                                      TABLE 17                                    __________________________________________________________________________    Mixture                                                                           Ex. 49                                                                            Mevimeox                                                                           Vicame                                                                            Vicaet                                                                            Vicabu                                                                            Vinon                                                                             Phase behavior                                   __________________________________________________________________________    142 89.0                                                                              11.0                 n 111-124 i                                        143 75.1 24.9     n 103-115 i                                                 144 57.3 42.7     cr 55 n 91-102 i                                            145 89.0  11.0    n 115-133 i                                                 146 75.3  24.7    n 119-132 i                                                 147 57.6  42.4    n 118-131 i                                                 148 88.6   11.4   n 120-130 i                                                 149 74.5   25.5   n 123-131 i                                                 150 56.5   43.5   n 130-135 i                                                 151 88.7    11.3  n 114-126 i                                                 152 74.6    25.4  n 110-121 i                                                 153 56.6    43.4  cr 58 n 111-119 i                                           154 86.5     13.5 n 82-106 i                                                __________________________________________________________________________

We claim:
 1. A polymerizable liquid-crystalline compound of the formulaI

    Z.sup.1 --Y.sup.1 --A.sup.1 --Y.sup.3 --M--Y.sup.4 --A.sup.2 --Y.sup.2 --Z.sup.2                                                 I

where Z¹ and Z² are radicals containing reactive groups via whichpolymerization can be effected, Y¹ -Y⁴ are a single chemical bond,oxygen, sulfur, --O--CO--, --CO--O--, --O--CO--O--, --CO--NR--,--NR--CO--, --O--CO--NR--, --NR--CO--O-- or --NR--CO--NR--, where atleast one of the groups Y³ and Y⁴ is --O--CO--O--, --O--CO--NR--,--NR--CO--O-- or --NR--CO--NR--, A¹ and A² are spacers having 2 to 30carbon atoms in which the carbon chain may be interrupted by etheroxygen, thioether sulfur or by nonadjacent imino or C₁ -C₄ -alkyliminogroups, M is a mesogenic group, R is C₁ -C₄ -alkyl.
 2. A polymerizableliquid-crystalline compound as claimed in claim 1, where at least one ofthe groups Y³ and Y⁴ is --O--CO--O--.
 3. A polymerizableliquid-crystalline compound as claimed in claim 1, where the mesogenicgroup M is a group of the formula Ia

    --(--T--Y.sup.5 --).sub.r --T--                            Ia

where T is a divalent saturated or unsaturated iso- or heterocyclicradical, Y⁵ is a radical as defined for Y¹ -Y⁴ or is --O--CH₂ --, --CH₂--O--, --CH═N--, --N═CH-- or --N═N--, r is 0, 1, 2 or 3,where theradicals T and Y⁵, in the case where r is >0, may be identical ordifferent.
 4. A polymerizable liquid-crystalline compound as claimed inclaim 1, where the mesogenic group M is a group of the followingformulae ##STR85## where each ring can carry up to three identical ordifferent substituents from the following group:C₁ -C₂₀ -alkyl, C₁ -C₂₀-alkoxy, C₁ -C₂₀ -alkoxycarbonyl, C₁ -C₂₀ -monoalkylaminocarbonyl, C₁-C₂₀ -alkylcarbonyl, C₁ -C₂₀ -alkylcarbonyloxy, C₁ -C₂₀-alkylcarbonylamino, formyl, halogen, cyano, hydroxyl and nitro.
 5. Apolymerizable liquid-crystalline compound as claimed in claim 1, wherethe radical pairs Z¹ and Z², Y¹ and Y², Y³ and Y⁴, and A¹ and A² are ineach case identical.
 6. A liquid-crystal composition comprisinga) atleast one compound as claimed in claim 1, which is optionally mixed withb) one or more compounds of the formula II

    Z.sup.3 --Y.sup.6 --A.sup.3 --Y.sup.7 --M--Y.sup.8 --P.sup.1II,

whereZ³ is a radical containing reactive groups via which polymerizationcan be effected, Y⁶ -Y⁸ are a single chemical bond, oxygen, sulfur,--O--CO--, --CO--O--, --O--CO--O--, --CO--NR--, --NR--CO--,--O--CO--NR--, --NR--CO--O-- or --NR--CO--NR--, where at least one ofthe groups Y⁷ and Y⁸ is --O--CO--O--, --O--CO--NR--, --NR--CO--O or--NR--CO--NR--, A³ is a spacer having 2 to 30 carbon atoms in which thecarbon chain may be interrupted by ether oxygen, thioether sulfur or bynonadjacent imino or C₁ -C₄ -alkylimino groups, P¹ is a radical selectedfrom the group of hydrogen, C₁ -C₃₀ -alkyl, C₁ -C₃₀ -acyl, C₃ -C₈-cycloalkyl unsubstituted or substituted by one to three C₁ -C₆ -alkyland where the carbon chain of the alkyl, acyl and cycloalkyl radicalsmay be interrupted by ether oxygen, thioether sulfur or by nonadjacentimino or C₁ -C₄ -alkylimino groups, and/or c) one or more compounds ofthe formula III

    P.sup.2 --Y.sup.9 --M--Y.sup.10 --P.sup.3                  III,

whereP², P³ are radicals selected from the group of hydrogen, C₁ -C₃₀-alkyl, C₁ -C₃₀ -acyl, C₃ -C₈ -cycloalkyl unsubstituted or substitutedby one to three C₁ -C₆ -alkyl, and where the carbon chain of the alkyl,acyl and cycloalkyl radicals may be interrupted by ether oxygen,thioether sulfur or by nonadjacent imino or C₁ -C₄ -alkylimino groups,Y⁹, Y¹⁰ are a single chemical bond, oxygen, sulfur, --O--CO--,--CO--O--, --O--CO--O--, --CO--NR--, --NR--CO--, --O--CO--NR--,--NR--CO--O-- or --NR--CO--NR--, where at least one of the groups Y⁹ andY¹⁰ is --O--CO--O--, --O--CO--NR--, --NR--CO--O or --NR--CO--NR--, M isa mesogenic group,where the mesogenic groups M of the formulae I, II andIII can be identical to or different from one another.
 7. Aliquid-crystal composition comprising one or more compounds of theformulae I, II and III as claimed in claim 6 and one or more chiralcompounds.
 8. A liquid-crystal composition as claimed in claim 6,comprising components a), b) and c) in a molar proportion based on thetotal amount of said components ofa) 1-98 mol %. b) 1-98 mol %, c)0.01-90 mol %,with the proviso that the total of the mol % of thecomponents is 100 mol %.
 9. A liquid-crystal composition as claimed inclaim 7, comprising components a), b) and c) in a proportion of from 60to 99.999% by weight and the chiral compound or chiral compounds in aproportion of from 0.001 to 40% by weight, in each case based on thetotal amount of components a), b) and c), and of the chiral compound orchiral compounds, with the proviso that the total of the percent byweight of the compounds is 100% by weight.
 10. A liquid-crystalcomposition comprising 10 to 100% by weight of the polymerizableliquid-crystalline compounds I, I and II and/or III as claimed in claim6, 0 to 90% by weight of other monomers and 0 to 50% by weight of one ormore chiral compounds, in each case based on the total weight of theliquid-crystal composition.
 11. A process for preparing one or morepolymerizable liquid-crystalline compounds of the formula I from claim1, where the two variables Y³ and Y⁴ are both --O--CO--O--, whichcomprises reacting one or more chloroformates of the formula IVa

    Z.sup.1 --Y.sup.1 --A.sup.1 --O--CO--Cl                    IVa

with one or more mesogen diols of the formula V

    HO--M--OH                                                  V

to give the symmetrical compound of the formula Ia

    Z.sup.1 --Y.sup.1 --A.sup.1 --O--CO--O--M--O--CO--O--A.sup.1 --Y.sup.1 --Z.sup.1                                                 Ia

or reacting in a first step a chloroformate of the formula IVa and in asecond step a chloroformate of the formula IVb

    Z.sup.2 --Y.sup.2 --A.sup.2 --O--CO--Cl                    IVb

with a mesogen diol of the formula V to give the asymmetrical compoundIb

    Z.sup.1 --Y.sup.1 --A.sup.1 --O--CO--O--M--O--CO--O--A.sup.2 --Y.sup.2 --Z.sup.2                                                 Ib.


12. 12. A liquid-crystalline compound of the formula II

    Z.sup.3 --Y.sup.6 --A.sup.3 --Y.sup.7 --M--Y.sup.8 --P.sup.1(II),

where Z³ is a radical containing reactive groups via whichpolymerization can be effected, Y⁶ is oxygen, sulfur, --O--CO--,--CO--O--, --O--CO--O--, --CO--NR--, --NR--CO--, --O--CO--NR--,--NR--CO--O-- or --NR--CO--NR--, Y⁷ and Y⁸ are each a single chemicalbond, oxygen, sulfur, --O--CO--, --CO--O--, --O--CO--O--, --CO--NR--,--NR--CO--, --O--CO--NR--, --NR--CO--O-- or --NR--CO--NR--, where atleast one of the groups Y⁷ and Y⁸ is --O--CO--O--, --O--CO--NR--,--NR--CO--O-- or --NR--CO--NR--, A³ is a spacer having 2 to 30 carbonatoms in which the carbon chain may be interrupted by ether oxygen,thioether, sulfur or by nonadjacent imino or C₁ -C₄ -alkylimino groups,P¹ is a radical selected from the group consisting of hydrogen, C₁ -C₃₀-alkyl, C₁ -C₃₀ -acyl, C₃ -C₈ -cycloalkyl unsubstituted or substitutedby one to three C₁ -C₆ -alkyl and where the carbon chain of the alkyl,acyl and cycloalkyl radicals may be interrupted by ether oxygen,thioether sulfur or by nonadjacent imino or C₁ -C₄ -alkylimino groups, Mis a mesogenic group, and R is a C₁ -C₄ alkyl group.
 13. A process forpreparing one or more liquid-crystalline compounds of the formula IIfrom claim 12, where the two variables Y⁷ and Y⁸ are both --O--CO--O--,which comprises reacting in a first step a chloroformate of the formulaIVc

    Z.sup.3 --Y.sup.6 --A.sup.3 --O--CO--Cl                    IVc

or a chloroformate of the formula VI

    P.sup.1 --O--CO--Cl                                        VI

and in a second step a chloroformate of the formula VI or achloroformate of the formula IVc with one or more mesogen diols of theformula V

    HO--M--OH                                                  V.


14. A process as claimed in claim 11, wherein the reaction is carriedout in the presence of an organic and/or inorganic base.
 15. A processfor producing coatings having a liquid-crystalline ordered state, whichcomprises applying one or more liquid-crystalline compounds as claimedin claim 1 and, optionally, further polymerizable compounds and chiralcompounds to a substrate, effecting a liquid-crystalline alignment, andthen polymerizing the compounds applied to the substrate.
 16. A coatedarticle obtainable by a process as claimed in claim
 15. 17. Acholesteric liquid-crystalline colorant comprising a liquid-crystalcomposition as claimed in claim
 7. 18. A pigment obtainable bysubjecting a liquid-crystal composition as claimed in claim 7 topolymerization and then comminuting the polymeric material to a pigmentparticle size.
 19. The polymerizable liquid-crystalline compound of theformula I of claim 1, wherein Z¹ and Z² are independently selected fromthe following groups: ##STR86##